Time-resolved ultrafast x-ray scattering from an incoherent electronic mixture

Abstract

Time-resolved ultrafast x-ray scattering from photo-excited matter is an emerging method to image ultrafast dynamics in matter with atomic-scale spatial and temporal resolutions. For a correct and rigorous understanding of current and upcoming imaging experiments, we present the theory of time-resolved x-ray scattering from an incoherent electronic mixture using quantum electrodynamical theory of light-matter interaction. We show that the total scattering signal is an incoherent sum of the individual scattering signals arising from different electronic states and therefore heterodyning of the individual signals is not possible for an ensemble of gas-phase photo-excited molecules. We scrutinize the information encoded in the total signal for the experimentally important situation when pulse duration and coherence time of the x-ray pulse are short in comparison to the timescale of the vibrational motion and long in comparison to the timescale of the electronic motion, respectively. Finally, we show that in the case of an electronically excited crystal the total scattering signal imprints the interference of the individual scattering amplitudes associated with different electronic states and heterodyning is possible.

arXiv comment18 pages

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Cited by in corpus (7)

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• Characterizing dissociative motion in time-resolved x-ray scattering from gas-phase diatomic molecules
• Ultrafast Molecular Frame Quantum Tomography
• Probing the Effect of Molecular Structure Saddling on Ultrafast Charge Migration via Time-Resolved X-ray Diffraction
• Theory of high-energy correlated multiphoton x-ray diffraction for synchrotron radiation sources